7.3.2 Boundary Conditions
may now be specified. Pick "Create Nodestring" tool from the tool palette. This tool is
used to identify the nodes along the edge of the model domain. Use the mouse pointer to
select the start point (node) of the semicircular open boundary. (The "Zoom" tool may be
used to help identify the start node.) Press and hold the <Ctrl> key and select the end
point (node) of the semicircular open boundary. Press <Enter>. The open boundary has
been defined by a single "nodestring". For open sea/offshore problems, where open
boundary is a full circle, similar procedure applies. For this example, we will next define
the coastline boundary using a single string. Proceed with the above selection procedure,
this time using the end point of the semicircle as the new start point. The new end point is
the start point of the semicircle. In some modeling situations, the user may want to assign
different reflection coefficients to sections of the coastline. If this is the case, a nodestring
must be created for each area of differing reflection coefficient. A new nodestring must
always begin with the end point of the previous string. The direction of nodestrings
should be specified such that when moving from the start point to the end point of the
nodestring, the modeled domain is on the left side of the nodestring, i.e. counter-
clockwise.
Defining Islands Boundaries. Island boundaries are defined in much the same
way as described above, with the following exceptions. Island nodestrings are created
such that the modeled domain is on the right side of the nodestring when moving from the
start point to the end point, i.e. counter-clockwise. A complete island boundary must
consist of two or more nodestrings, as SMS does not allow a single nodestring to begin
and end on the same node. Islands should be defined after all open and coastal boundaries
have been defined.
Assigning Reflection Coefficients.
Pick "Select Nodestring" tool. A small
selection area (box) should appear in the center of each nodestring. Place the pointer on
the selection box for the open boundary and select it. Go to the "RMA2" menu and select
55
Previous Page
